Zoom optical system, imaging lens device, and digital apparatus

Abstract

A reflecting prism (PR 1 ) and a reflecting prism (PR 2 ) each adapted to bend an incident ray at a predetermined angle for reflection are arranged in such a manner that an incident surface of the reflecting prism disposed on a side of a subject on an optical path and the exit surface of the other reflecting prism are aligned substantially parallel to each other. The incident surface or the exit surface of at least one of the reflecting prisms has an optical power. At least one lens group including one or more lens element is arranged between the two reflecting prisms in such a manner that the optical axis of the lens group is coincident with the axis of the optical path between the two reflecting prisms. At least one lens group is moved in the direction of the optical axis thereof. Thus, provided are a thin and superfine zoom optical system, an imaging lens device incorporated with the zoom optical system, and a digital apparatus loaded with the imaging lens device.

1. A zoom optical system comprising:
 a first reflecting prism configured to bend an incident ray at about 90 degrees by reflection, and having an incident surface disposed on a subject side of an optical path and an exit surface disposed on an object side of said optical path; 
 a second reflecting prism configured to bend an incident ray at about 90 degrees by reflection, and having an incident surface disposed on the subject side of an optical path and an exit surface disposed on the object side of said optical path, and 
 at least one lens group including one or more lens elements arranged between the exit surface of the first reflecting prism and the incident surface of the second reflecting prism, 
 the incident surface of the first reflecting prism, and the exit surface of the second reflecting prism being aligned substantially parallel to each other, the incident surface or the exit surface of the first reflecting prism having an optical power, and, if the incident surface of the first reflecting prism has an optical power, the incident surface of the second reflecting prism has an optical power or, if the exit surface of the first reflecting prism has an optical power, the exit surface of the second reflecting prism has an optical power, wherein the reflecting surface of the reflecting prisms are flat, 
 an optical axis of the lens group and an axis of the optical path between the first and second reflecting prisms being coincident with each other, the lens group being movable along the optical axis thereof for zooming. 
 
   
   
     2. The zoom optical system according to  claim 1 , wherein
 the incident surface and the exit surface of the each of the first and second reflecting prisms have an optical power. 
 
   
   
     3. The zoom optical system according to  claim 1 , further comprising an aperture stop on the side of the exit surface of the first reflecting prism disposed on the subject side on the optical path, wherein
 at least the incident surface of the first reflecting prism has a negative optical power. 
 
   
   
     4. The zoom optical system according to  claim 1 , wherein
 at least two lens groups are arranged between the first and second reflecting prisms, the at least two lens groups each including one or more lens elements. 
 
   
   
     5. The zoom optical system according to  claim 4 , wherein the at least two lens groups are moved along the optical axis thereof for zooming. 
   
   
     6. The zoom optical system according to  claim 1 , wherein the at least one lens group is moved in a direction of the optical axis thereof for focusing. 
   
   
     7. The zoom optical system according to  claim 1 , wherein
 at least one of the first and second reflecting prisms is made of a resin material. 
 
   
   
     8. The zoom optical system according to  claim 7 , wherein
 a water absorption coefficient of the resin material constituting the reflecting prism is 0.01% or smaller. 
 
   
   
     9. The zoom optical system according to  claim 1 , wherein at least one of the first and second reflecting prisms is produced by glass molding. 
   
   
     10. The zoom optical system according to  claim 1 , further comprising an optical device having an optical power on the optical path between the incident surface of the first reflecting prism, and the exit surface of the second reflecting prism. 
   
   
     11. The zoom optical system according to  claim 1 , wherein the second reflecting prism has an infrared ray blocking function to reduce an infrared component included in the incident ray. 
   
   
     12. An imaging lens device comprising a zoom optical system including:
 a first reflecting prism configured to bend an incident ray at about 90 degrees by reflection, and having an incident surface disposed on a subject side of an optical path and an exit surface disposed on an object side of said optical path; 
 a second reflecting prism configured to bend an incident ray at about 90 degrees by reflection, and having an incident surface disposed on the subject side of an optical path and an exit surface disposed on the object side of said optical path, and 
 at least one lens group including one or more lens elements arranged between the exit surface of the first reflecting prism and the incident surface of the second reflecting prism, 
 the incident surface of the first reflecting prism, and the exit surface of the second reflecting prism being aligned substantially parallel to each other, the incident surface or the exit surface of the first reflecting prism having an optical power, and, if the incident surface of the first reflecting prism has an optical power, the incident surface of the second reflecting prism has an optical power or, if the exit surface of the first reflecting prism has an optical power, the exit surface of the second reflecting prism has an optical power, wherein the reflecting surface of the reflecting prisms are flat, 
 an optical axis of the lens group and an axis of the optical path between the first and second reflecting prisms being coincident with each other, the lens group being movable along the optical axis thereof for zooming, and 
 the zoom optical system having such a configuration as to form an optical image of a subject on a predetermined imaging plane of the zoom optical system. 
 
   
   
     13. A digital apparatus comprising:
 an imaging lens device; 
 an image sensor; and 
 a functioning section which causes the imaging lens device and the image sensor to execute at least one of shooting a still image of the subject, and shooting a moving image of the subject, 
 the imaging lens device including a zoom optical system having: 
 a first reflecting prism configured to bend an incident ray at about 90 degrees by reflection, and having an incident surface disposed on a subject side of an optical path and an exit surface disposed on an object side of said optical path; 
 a second reflecting prism configured to bend an incident ray at about 90 degrees by reflection, and having an incident surface disposed on the subject side of an optical path and an exit surface disposed on the object side of said optical path, and 
 at least one lens group including one or more lens elements arranged between the exit surface of the first reflecting prism and the incident surface of the second reflecting prism, 
 the incident surface of the first reflecting prism, and the exit surface of the second reflecting prism being aligned substantially parallel to each other, the incident surface or the exit surface of the first reflecting prism having an optical power, and, if the incident surface of the first reflecting prism has an optical power, the incident surface of the second reflecting prism has an optical power or, if the exit surface of the first reflecting prism has an optical power, the exit surface of the second reflecting prism has an optical power, wherein the reflecting surface of the reflecting prisms are flat, 
 an optical axis of the lens group and an axis of the optical path between the first and second reflecting prisms being coincident with each other, the lens group being movable along the optical axis thereof for zooming, and 
 the zoom optical system having such a configuration as to form an optical image of a subject on a predetermined imaging plane of the zoom optical system. 
 
   
   
     14. The digital apparatus according to  claim 13 , wherein a display surface of a display provided in the digital apparatus, and a light receiving surface of the image sensor are parallel to each other, and a longer side of the display surface and a longer side of the light receiving surface are parallel to each other.